Throughout the industrialized world there are deposits of contaminated soil which pose a hazard. Ground water enters these contaminated soils, dissolves and carries some of the contaminants into drinking water supplies. The contaminants include such materials as harmful organic compounds and soluble heavy metals. In some cases the soils are contaminated with radioactive wastes.
In some serious cases, contaminated soils are removed and treated in furnaces to produce vitrified masses of material. When contaminated soil is vitrified, its density is increased and its volume is reduced. Additionally, organic compounds are typically incinerated and rendered harmless. When a mass of contaminated soil is vitrified, it can be safely buried in the earth because any heavy metal components of the soil are made substantially unleachable in ground water.
In addition to contaminated soils, there are other hazardous objects which require safe disposal. For, example obsolete military devices such as fuses and chemical warfare apparatus need to be destroyed in a cost-effective way. In many of these cases, for purposes of maintaining secrecy, there is a need to obliterate any discernible features or characteristics of the devices. Disposal of such devices in a vitrified soil medium has been found to be technically and economically viable.
Another area of waste treatment involves pyrolysis of certain small quantities of radioactive materials. In these cases, it is desirable to avoid transporting the radioactive materials to a waste treatment facility. Instead, it is useful to provide a portable waste treatment unit which can be transported to the location of the radioactive material. This, of course requires that such waste treatment equipment be compact and readily transportable. Ideally such a treatment unit might have a glove-box configuration.
Whenever these waste vitrification, incineration and pyrolysis methods are practiced, a quantity of complex gaseous effluents are produced. These effluents cannot simply be released to the atmosphere. They must be reduced into more simple components and then treated to eliminate any possible toxicity. Typically, the conversion of a complex effluent into simple treatable components requires addition of energy to the effluent. In other words, the effluent must be incinerated and oxidized.
Ironically, whenever a complex effluent is oxidized, there has heretofore been a need to add a certain mass of energy bearing material to the effluent stream. Typically, this energy bearing material is a combustible mixture such as propane or natural gas and oxygen. This results in a need to treat a greater mass of gas than that which emerges as the original effluent.
Treatment of gases that are the products of an effluent oxidization process is costly. It is desirable therefore to develop a process in which the quantities of gases needing treatment are held to a minimum.
Some prior art methods have been directed toward that goal. For example, some systems have employed plasma arc torches as a source of energy to accomplish incineration of effluent without producing additional products of combustion.
In this type of system a plasma gas such as argon or oxygen is passed through a plasma arc torch and injected at very high temperature into a stream of effluent. Heat is transferred to the effluent stream from the heated plasma gas and the temperature of the effluent rises accordingly. These plasma arc systems have some obvious advantages over fuel based incineration systems in that a lower mass of material needs to be introduced into the effluent stream. This, of course, means that a lower mass of incinerated and oxidized gas needs to be treated to eliminate toxicity. One example of these prior art systems is described in Proceedings of the International Topical Meeting on Nuclear and Hazardous Waste Management Spectrum '96, Aug. 18-23, 1996 in a paper entitled "The PERC Process: Existing and Potential Applications for Induction Coupled Plasma Technology in Hazardous and Radioactive Waste Treatment", presented by A. S. Blutke, J. S. Vavruska and J. F. Serino.
However, even these improved prior art plasma arc systems add mass to the effluent stream. The argon or oxygen or other plasma gas is introduced into the effluent stream and increases its mass.
It is a goal of the present invention to provide a method of adding energy to an effluent stream in a manner which will produce a desired incineration and oxidation of the effluent while not adding to its mass.
It is a further goal of the present invention to provide such a method which can be practiced with apparatus which is compact and inexpensive.